1. Field of Invention
The present invention relates to a gas generator for a restraining device such as an airbag system for a vehicle.
2. Description of Related Art
In a pyrotechnic gas generator using a solid gas generating agent, a filter is used for collecting combustion residues generated during actuation.
Combustion gas generated from the gas generating agent passes through the filter or collides therewith before the combustion gas is discharged from the housing, thereby causing the residues contained in the combustion gas to adhere to the filter and also reducing the temperature of the combustion gas.
For this reason, after actuation of the gas generator, the heat of the residues and the combustion gas is transferred to the filter and the filter is heated to a high temperature.
The filter is usually arranged inside the housing in direct contact with the housing or in indirect contact with the housing, being supported by another member. After actuation, the heat from the filter or combustion residues is gradually transferred to the housing. As a result, temperature of the housing rises.
The temperature of the housing rises slowly due to heat transfer from the filter or combustion residues after actuation of the gas generator, compared with the usual actuation time (in figures of milliseconds) of the gas generator. For example, in 2 to 3 minutes, the housing attains high temperature and therefore, when the deployed airbag is deflated and comes into contact with the housing, the airbag fabric may be melted by the heat. Further, if the occupant leans on a steering wheel after the airbag is deployed, the occupant can be adversely affected by the excessive increase in housing temperature.
Therefore, in the pyrotechnic gas generators, it is necessary to inhibit the excessive increase in temperature of at least the housing facing the occupant after actuation.
In U.S. Pat. No. 7,891,703, a retainer 11 disposed inside an inflator 12 covers the upper surface of a combustion chamber in which a filter 5 and a gas generating agent 4 are accommodated, and an engaging section 11a engaging with the upper end of a tube 6 is provided in the central portion of the retainer.
Further, a plurality of holes 11b is formed in the retainer 11, the difference in pressure between the inside and outside of the combustion chamber surrounded by the retainer 11 is reduced, the deformation of the retainer during actuation is inhibited, and the combustion gas leakage from the abutment surface of the filter 5 and the retainer 11 is prevented.